Clinical assessment of patients with disorders of consciousness

Abstract

The study of pathological impairments of consciousness, as they can appear in severely brain injured patients, can be particularly useful to better clarify cognitive processes and cerebral substrates which underlie consciousness. In this review, we will introduce the disorders of consciousness that can be presented by severely brain-injured patients and the behavioural scales that can be used to assess their level of consciousness. We will also discuss the difficulty to assess and detect remnant cognitive functioning in these patients. The study of pathological impairments of consciousness, as they can appear in severely brain injured patients, can be particularly useful to better clarify cognitive processes and cerebral substrates which underlie consciousness. The vegetative state is characterized by a preservation of the arousal level but also by the absence of any sign of consciousness of the environment and of oneself (e.g., absence of oriented responses to sensory stimulations or absence of significant verbal production) (The Multi-Society Task Force, 1994). The patient in a minimally conscious state, on the contrary, demonstrates inconsistent, primary but reproducible signs of consciousness of the environment (e.g., visual pursuit of an object moving in the patient’s visual field) and of oneself (e.g., accurate response to verbal order suggesting an interaction between the patient and his/her surroundings) (Giacino et al., 2002). Both populations mentioned here are therefore particularly useful to study the concept of consciousness via the progressive recovery of the most basic aspects of consciousness, and the behavioural, cognitive and cerebral signs which accompany them. In this review, we will introduce the disorders of consciousness that can be presented by severely brain-injured patients and the behavioural scales that can be used to assess their level of consciousness. We will also discuss the difficulty to assess and detect remnant cognitive functioning in these patients.